Method of drying ammunition primers



Nov. 14, 1950 F. oLsEN METHOD oF DRYING ArmuNITIoN PRIMERS Filed Feb. 24, 1944 Ens HTT'QRNEYS Patented Nov. 14, 1950 2,529,704 METHOD F DRYING AMMUNITION PRIME Fredrich Olsen, Alton, Ill., assignor to Olin Industries, Inc., East Alton, Ill., a corporation of Delaware Application February 24, 1944, Serial N o. 523,693 13 Claims. (Cl. 34-4) This invention relates generally to the manufacture of ammunition and particularly to that aspect of ammunition manufacture which involves the drying of loaded primers.

In the manufacture of ammunition, the for-'f mulated priming composition is conventionally loaded intoV the primer cups while the priming composition is in the form of a paste containing on the order of 10 to 12% of water. The loading of the primer cups is a hazardous operation but the presence of substantial amounts of moisture in the mixture effectively desensitizes it so that the hazard is materially reduced. Before the round of ammunition is loaded with propellant, however, it is essential to reduce the moisture content of the priming composition to a maximum of about 0.5% in order to restore its sensitivity.

In accordance with the conventional practice, the primer cups (or primer cavities in the case of rim-tire ammunition) are loaded with moist primer composition in automatic or semi-automatic machinery. After being inspected the loaded primer cups are deposited in a suitable dryer in which the excess moisture is extracted. The type of dryer commonly employed for drying primers is an oven in which the loaded primers are deposited in substantial volume and the temperature of the dryer elevated to a point such as to evaporate themoisture from the priming composition. Care L'must be exercised, however, that the temperature in such a dryer does not exceed the point at which the primer composition or any ingredient-thereof.isliable togignite or detonate,

-because with the primers deposited in bulk in such an o ven the entire device becomes a potential bomb and the ignition or detonation of a single primer is likely to explode the-entire organization with consequent damage and, injury to environs. Mindfulk of the hazard which is involved in such a drying operation, the explosives industry has heretofore been careful to limit the maximum temperatures to which such dryers are subjected, the conventional maximum temperature being 155 F.

Drying operations conducted in such manner,

however, require extended periods of time, generally at least seven hours. Due to the bulk arrangement of the primers in such a dryer some primers dry out before others, and accordingly the continued heating of the already-dried prim'- ers, while others are continuingtto dry, introduoes a special hazard which itis diillcult to avoid because incompletely dried primers are too insensitive to be useful.

mine its sensitivity will immediately be recognized because, in the process of testing, the primer is destroyed. Theonly tests which can be made, therefore, must be made uponv primers selected at random from a given batch and the results obtained from the tested group determine the acceptance or rejection of the batch. Such does not preclude the possibility of the presence in a given batch of primers or individual ones which may not have been suillciently dried to be opera.- tively sensitive. This demands that the drying operation be carried on to such an extent that there is no possibility of presence in theA batch of an undried primer and such, of course, increases the hazard of the drying operation. l

The object of the present invention, generally stated. is to provide a ,process of drying primers whereby each individual primer is assuredly subjected to substantially identical drying inuences.

A further object of the present invention is to expedite the drying of loaded primers.

Another object of the present invention is to minimize the hazard involved in primer drying' operations.

Other objects will become apparent to those skilled -in the art when the following description is read and understood.

In accordance with the present invention, generally stated, the loaded primer cups containing The impossibility of testing a primer to deter-'55 moist primer composition are arranged in trays of convenient size as the loaded cups emerge from the conventional primer loading apparatus. The trays may be of a size and shape most convenient for handling in the drying apparatus available, as, for example, about three inches by fifteen inches, which will accommodate about fifteen hundred caliber .30 primers, but it will be understood that larger or smaller trays may be used if desired. In loading the primers into the trays it is desirable to arrange them on end, preferably with the anv'il end up (or, in the case of rimflre ammunition, with the open end up) and in a single layer. Such orientation of the loaded primer cups enables inspection of the primer prior to and after the drying operation without necessitating intermediate rehandling of the individua1 primer. Furthermore, the anvil end up orientation is proper for feeding into the machines conventionally employed for inserting the loaded primers into cartridge cases. Although the primers may usually be adequately dried with the anvil end down or on side, the drying operation is frequently facilitated by 'arranging them on end, open end up.

The primers thus arranged in trays, or other- 3 wise segregated into groups are, according to the present invention, passed through a dryer in a single layer. The present invention contemplates that the dryer be energized with near infra red light so controlled in intensity as to elevate the temperature of the primers to the desired maximum immediately upon entrance into the dryer and thereafter to maintain substantially the same temperature, without, however, at any time subjecting the primers to local "hot spots. In order to accomplish the initial rapid elevation of the ,temperature to the desired point, the intensity of endless Vconveyor belt travels. The primers, ar-

ranged in trays or in segregated groups are placed upon the conveyor belt in a single layer, and carried thereby from one end o! the enclosure to the other. Within the enclosure a series of sources of near infra red light is arranged so that the greatest intensity of irradiation exists at the entrance end of the enclosure, and therebeyond the intensity of' irradiation at the path of travel of the primers is lgradually diminishing.

A suitable apparatus is shown somewhat diagrammatically in the accompanying drawings, in which:

Figure 1 is a longitudinal sectional view oi' the drying apparatus showing a series of trays laden with loaded primers en route through the dryer;

Figure 2 is a sectional view taken along line 2-2 of Figure 1 and showing the relative positions of the series of sources of near inira red light; and

Figure 3 is a plan view of a tray for holding the primers during the drying operation. A

In the apparatus shown in the accompanying drawings, an enclosure I having side walls 2, 3 and end walls 4, 5 is arranged above a conveyor belt 6 so as to extend slightly beyond the edges of the conveyor belt. The end walls 4 and 5 are provided with openings 1, -3 of suicient size to permit the passage of the conveyor belt laden with trays of the character hereinbefore described. It is desirable that the openings I and 8 be no larger than necessary to permit thepassage of the belt and trays.

The conveyor belt 6 is mounted upon suitable pulleys and driven at a substantially constant speed from left to right as indicated by the arrow in Figure 1, the upper reach thereof traveling upon a suitable supporting table 9.

Any suitable enclosing hood II) may be provided over the enclosure I and may be equipped with a. vent II )provided with a suitable exhaust fan, not shown. v

Arranged within the enclosure I is a plurality of sources of near infra red light I2 and I3. In the embodiment shown in the drawings the sources of near infra red light I2 adjacent the entrance end of the dryer are Z50-watt infra red lamps of the character readily obtainable upon the market and having self contained reilectors. In the embodiment shown nine such lamps I2 are utilized in vthree rows so that .the lamps nearest the entrance end of the dryer are, for example, six inches above the surface of conveyor 6, the next row nine inches and the third row twelve inches above the conveyor belt. By such an arrangement a primer situated upon the belt immediately below the first lamp to which it is exposed is under a greater intensity of irradiation than such primer will be when it reaches a position immediately below the second lamp and is under still` less intensity of irradiation when it reaches a position below the third lamp.

Beyond the series of lamps I2 is a series of inira red lamps I3 which are the usual inIra red lamps of commerce of, for example, 25u-watt capacity. Such lamps are arranged within suitable gold plated reflectors of the type usually employed in connection with infra red lamps.

The series of infra red lamps. are arranged so as to uniformly distribute the irradiation crosswise of the conveyor belt, but, as clearly shown in Figure 1, each successive pair of lamps I3 is arranged at an elevation slightly above that of its predecessor, thereby to gradually diminish the intensity of irradiation upon the surface oi the conveyor beltv as theexit B'is approached. For example, the pair o! lamps I3 nearest the entrance 'I may be arranged at about six inches above the surface of the'conveyor belt while the pair of lamps nearest the exit 8 may be as much as twenty-four inches above the surface of the conveyor belt. a

Upon the upper reach of the conveyor belt 6 a plurality of trays Il are shown. One such tray is shown in plan view in Figure 3. The trays Il may be of any convenient size and formed of any suitable material, such, for example, as wood, metal, asbestos, or a moulding composition which is not deteriorated by exposure to infra red light at the temperatures encountered within the dryer. Arranged in each ot the trays I4 are as many loaded primer cups I5 as the tray will accommodate. The laden trays are placed upon the conveyor belt at the left of entrance 'I and the speed of the conveyor belt is regulated in accordance with the temperatures to be encountered within the enclosure I and the composition of priming mixture so that the primers remain exposed to the irradiation within the enclosure for a period of time suiilcient to accomplish the desired drying which may be from ten minutes to an hour.

As an arunct to the enclosure I a compartment I6 may be provided and any suitable means for circulating cooling air in the compartment I6 may be provided so that as primers emerge from exit 8 they will be substantially 'cooled before reaching the right end of the conveyor belt. where the trays I4 are removed, further inspected if desired,.and passed on to the primer inserting machines.

If desired, one of the side walls such as 3 of the enclosure I may be provided with a plurality of openings I1, each having a suitable door or other closure I8 through which access to the interior of the dryer may be obtained when lt is necessary to service the equipment.

The enclosure I may be dispensed with if the drying apparatus is so situated that temperature fluctuations of the primers undergoing drying are not encountered, as would be the case where the apparatus is exposed to occasional cold drafts. y

With an apparatus of the character disclosed the drying of the loaded primers may be accomplished as a continuous operation having at one of the irradiation from the lamps I2 is such that the .temperature of the primers is elevated' to 95 C. within the iirst two minutes of ex- DOSUITC- In the case of caliber .30 primers charged with a priming composition composed as follows: Parts by weight TNT Antimony sulphide 17 Potassium chlorate 53 Lead sulphacyamde 25 Gum 0.2

and containing, as charged, 9-12% of moisture, the lamps I2 were so adjusted as to elevate the temperature of the primers to 75 C. in the period of time they are exposedin the field of irradiation of lamps I2, and the lamps I3 adjusted so as to maintain said temperature while the primers are4 passing through enclosure I. With 'the speed of the conveyor 6 regulated so that the primers remained exposed to such irradiation within the enclosure I for as brief a period as three minutes, the primers have been dried to such an extent as to pass the conventional drop test requirements, i. e., no misflres at a fifteeninch drop of a four-ounce ball.

In production operations of this character, however, it is economically desirable to allow a liberal factor of safety and consequently the minimum possible drying period is seldom feasible for commercial operations. In commercial dry- -ing operations on loaded primers of the character above specified where the lamps I2 and I3 were adjusted so as to achieve and maintain a. temperature of 75 C. the speed of the conveyor belt was adjusted so that the primers remained within the enclosure I under irradiation for a period of twelve minutes and the moisture ,content of the primer mix was reduced to about 0.1%.

The accelerated drying of the present invention has no deleterious effeet upon the sensitivity of the primers. For example, sensitivity and ballistics tests upon primers dried as just described duplicated the results obtained from primers loaded from the same ybatch of priming mix which had been dried in the heretofore conventional manner in a vacuum oven for a period of eight hours.

As illustrating the effect which a change in the proportions of an inert ingredient may have upon the drying time, the same composition as that described above but containing double the gum content, required thirty-five minutes of exposure within the enclosure I at a temperature of 80 C.

In selecting the maximum temperature to which the primers will be exposed within the dryer, the composition of'the primer can not be ignored. For example, in the case of primers containing trinitrotoluene, which melts at 80.82 C., the subjection of the primers during the drying operation to temperatures of 81 C. or above lowered the sensitivity enough to produce occasional misres. Accordingly in the drying of primers containing TNT it is important that the primers be subjected at no time to a radiation of such intensity as will elevate their temperature above 80 C.

a tIn another instance, a composition consisting o Parts by weight Diazodinitrophenol 15 Barium nitrate 35 I'etrazene 3 Antimony sulphide 17 Lead peroxide 20 Calcium silicide 10 Gum 0.2

and containing, as charged, 1012% of moisture, was adequately dried utilizing a temperature of C. (reached in the field of irradiation of lamps I2) and adjusting the speed of the conveyor so that the primers remained under irradiation for a period of twenty minutes.

It will be understood, of course, that the higher the temperature to which the primers are exposed within the dryer the shorter may be the duration of the treatment.

As illustrating the safety of the operation of drying primers in the manner hereinbefore described, a tray was laden with primers oriented as hereinbefore described with the neighboring primers in contact with each other. Black powder was placed over the center of the group, covering about forty primers. The black powder was ignited. While most 'of the primers went oi! it was a process of burning rather than of detonation, as shown by the fact that the primer anvils remained in their cups in most instances and the wooden tray was not damaged. In another experiment a number of primers were arranged in the form of a rectangle on a tray, the rectangle being about one inch by ten inches and the neighboring primers being in contact one with the other. Black powder was placed over the primers at one end of the rectangle and ignited. A

While the primers which were covered with black powder burned, the others remained unaifected. Thus it is demonstrated that even after ignition of one or more primers occurred within the dryer such would not cause detonation of all the primers being dried, and would not, in fact, cause many of them to burn. The neighboring primers to the one ignited might burn but the ignition would in no event extend beyond the connes of a single tray or the confines of a similar segregated group.

It will be understood, ofcourse, that the expression near infra. red light as used herein contemplates light having a wave length of between 6000 and 20,000 angstrom units such as is obtainable from the use of commercially available infra red or tungsten filament electric bulb.

For the purpose of the present invention the most useful wave lengths are between 8000 and 20,000 angstrom units.

In the foregoing specification and the appended claims, where reference is made to primers or primer cups it will be understood that the primer cavity of a rim-fire cartridge case is contemplated, as well as the usual primer receptacle for center-fire ammunition.

From the foregoing description it should be apparent that the present invention accomplishes. its objects and that valuable improvements are made in the safety, speed, and uniformity of drying ammunition primers. While one embodiment of a suitable apparatus has been fully described, it is to be distinctly understood that the invention is not limited to the details of the apparatus described but that many modifications and variations will naturally present themo1' the appended claims.

Having thus described the invention, what I l claim is:

A 1. In the art of making ammunition primers,

I the process comprising, providing primer cups loaded with wet priming composition, arranging the loaded cups in a single layer, passing the loaded cups through a zone irradiated with near infra red light of an intensity such as to elevate the temperature of the primers immediately to at least 70 C. and maintaining cups under the near infra red irradiation of intensity such as to maintain but not substantially exceed said initial temperature for at least three minutes.

2. In the art of making ammunition primers, the process comprising, providing primer cups loaded with /wet priming composition, arranging the loaded cups upon a continuously moving conveyor in a single layer, moving the laden conveyor through a zone irradiated with near infra red light of an intensity such as to immediately elevate the temperature of the primers to at least 70 C. and maintaining cups under the near infra red irradiation of intensity such as to substantially maintain said initial temperature for at least three but'not more than about thirtyve minutes.

3. In the art of making ammunition primers,

' the process comprising, providing primer cups loaded with wet priming composition, arranging the loaded cups in a single layer on end and in segregated groups, and passing the segregated groups of oriented cups through a zone irradiated with near infra red light of an intensity such as to elevate the temperature of the primers to at least 70 C. and maintaining cups under the near infra red irradiation of intensity such as to substantially maintain said temperature for at least three minutes.

4. In the art of making ammunition primers,

` the process comprising, providing primer cups loaded with wet priming composition, arranging the loaded cups in a single layer on end in trays, and passing the laden trays through a zone irradiated with near infra red light of an intensity such as to elevate the temperature of the primers to at least 70C. and maintaining cups under the' near infra red irradiation of intensity such as to substantially maintain said temperaturefor at least three minutes.

5. In the art of making ammunition primers, the process comprising, providing primer cups loaded with wet priming composition, arranging the loaded cups in a single layer on end, passing the oriented cups through a zone irradiated with near infra red light of an intensity such as to elevate the temperature of the primers immediately to at least 70 C. to 95 C. and maintaining cups under the near infra red irradia` tion of intensity such as to substantially maintain said temperature for at least three and not over thirty-live minutes.

6. In the art of making ammunition primers, the process comprising, providing primer cups loaded with wet priming composition, arranging the loaded cups upon a continuously moving conveyor in a single layer on end and moving theiladen conveyor through a zone, passing the oriented cups through a zone irradiated with near infra red light of an intensity such as to elevate the temperature of the primers to at least 70 C. to 95 C. and maintaining cups under the near infra red irradiation of intensity such as 8 to substantially maintain said temperature for at least three minutes.

7. In the art of making ammunition primers, the process comprising, providing primer cups loaded with wet priming composition, arranging the loaded cups in a single layer on end and in segregated groups, and passing the segregated groups of oriented cups through a zone irradiated with near infra red light of an intensity such as to elevate the temperature of the primers to at least 70 C. to 95 C. and maintaining cups under the near infra red irradiation of "intensity such as to substantially maintain said temperature for at least three minutes.

8. In the art of making ammunition primers, the process comprising, providing primer cups loaded with wet priming composition, arranging the loaded cups in a single layer on end in trays, and passing the laden trays through a zone irradiated with near infra red light of an intensity such as to elevate the temperature of the primers to at least 70 C. to 95 C. and maintaining cups under the near infra red irradiation of intensity such as to substantially maintain said temperature for at least three minutes.

9. In the art of making ammunition primers, the process comprising, providing primer cups loaded with wet priming composition, arranging the loaded cups in a single layer, and passing the oriented cups into a zone irradiated with near infra red light of an intensity such as to immediately elevate the temperature ci the primers to a temperature ofbetween '70 C. and 95 C., moving the primers through a continuously irradiated zone of gradually diminishing intensity, and removing the primers from the irradiated zone when the moisture content thereof has been reduced to about 0.5% or below.

10. In the art of making ammunition primers, the process comprising, providing primer cups loaded with wet priming composition, arranging the loaded cups in a single layer, and passing the oriented cups into a zone irradiated with near infra red light of an intensity such as to immediately elevate the temperature of the primers to a temperature of between 70 C. and C., moving the primers through a continuously irradiated zone of gradually vdiminishing intensity, but of sufficient intensity to maintain the primers at said temperature, and removing the primers from the irradiated zone when the moist-ure content thereof has been reduced to about 0.5% or below.l

1l. A method of making and treating ammunition primers which comprises. providing primer cups loaded with primer composition having a moisture content exceeding 10%, arranging a limited number of said primer cups as a compact group in a single layer with the open ends thereof upwardly, projecting light having a wave length between 8,000 and 20,000 ang-strom units downwardly to provide a zone of infra-red radiation, moving said group of loaded primer cups into said irradiated zone, said projected light having an intensity such that the heat developed on the surface of the primer cups and on the surface of the composition amounts to 70 to 95 degrees centigrade as the cups enter said zone, moving said group or primer cups within said irradiated zone while maintaining the light intensity impinging thereon such as to maintain said temperature, and adjusting the rate of movement of the primer cups to remove said group from said irradiated zone with a total exposure' period of less than thirty-ve minutes whereby the moisture content of the primer composition is reduced to at least .5%. 12. A method of making and treating ammu- .nition primers rwhich comprises, providing primer I cups loaded with primer composition having a in said irradiated zone while maintaining a. light intensity impinging thereon such as to maintain said temperature, adjusting the rate of movement of the primer cups to remove the same from the irradiated zone within an elapsed period of less than thirty-five minutes whereby the moisture content of the primer composition is reduced to less than .5%, and cooling the primer cups and composition as they emerge fr om the irradiated zone.

13. A method of making and treating ammunition primers which comprises, providing primer cups loaded with primer composition having a moisture content exceeding 10%, assembling a limited number of said primer cups into a group and in a single layer, establishing an irradiation zone having a wave length between 6.000 and 20,000 angstrom units, moving said group of loaded primer cups into said irradiated zone, said irradiated zone having an intensity such that the heat developed on the primer caps and on the composition amounts to at least 70 degrees centigrade as the cups rst enter said zone, continuously moving said group of primer cups within the irradiated zone while maintaining a light intensity impinging thereon such as to maintain said temperature, and moving the primer cups at such a rate as to remove the primer cups from the irradiated zone within an elapsed period of less than thirty-iive minutes whereby the moisture contents of the primer cups has been reduced to less than .5%.-

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS OTHER REFERENCES Publication, scientmo American. sept. 1941, 

